Apparatus for welding



Dec. 12, 1944.

M. S. CLARK APPARATUS FOR WELDING Original Filed May 22, 1941 4Sheets-Sheet 1 MALCOLM .5. CLARK Dec. 12, 1944. M. s. CLARK APPARATUSFOR WELDING Original Filed May 22, 1941 4 Sheets-Sheet 2 W m M m. c & M,L O C M p M H. mm! AW I w I w w P WWW,

Dec. 12, 1944.

M. s. CLARK 2,365,148

APPARATUS FOR WELDING Original Filed May 22, 1941 4 Sheets-Sheet 3 I34I36 42 I30 #56 Swarm ton MA L COLM So CLARK Dec. 12, 1944. M. s; CLARKAPPARATUS FOR WELDING Original Filed May 22, 1941 4 Sheets-Sheet 4Smart/f CONTROL (Four HA/v0) SOLE/VOID VALVE- (70mm CanTkaA) CONT/70L sELEc 7/9005 TRANSFQRNER Comma/L F/GHJ' art/0mm MALCOLM S. CLARA x w uPatented Dec. 12, 1944 UNITED STATES PATENT OFFICE APPARATUS FOR WELDINGMalcolm S. Clark, Warren, Ohio, a ssignor to The Federal Machine andWelder Company Original application May 22, 1941, Serial No.

394,595. Divided and this application September 25, 1943, Serial No.503,778

6 Claims.

This invention relates to welding methods and apparatus, and, moreparticularly is concerned Heretofore, in spot welding apparatus ithasbeen the standard practice to provide a pair of electrode dies whichare mounted for relative movement to and from each other. Usually, thelower die is mounted on a stationary, but vertically adjustable support,and the upper die is carried upon a slide or arm which is moved up anddown by an air motor or other suitable means. It has been proposedheretofore to support the upper die in a cushioned manner on the slideor arm. For example, the die may be held on a slide by a second airmotor or cushion, or may be resiliently positioned on the slide with theaid of metal springs.

Welding apparatus of the type described is open to the objection thatthe friction and inertia of the die carrier are comparatively high sothat the dies do not properly follow and engage the work during thewelding operation. This is particularly true with spot welding apparatusemployed to make an interrupted spot weld (sometimes called persistenceor pulsation welding). With known structures, once the 'dies have engaged with opposite sides of the work and the work oftens between thedies due tothe flow of current through the work, the dies do notsoftened surface of the work throughout the entire duration of thewelding operation. The result may be a burning of the metal, and, in allevents, a failure to obtain the best possible type of weld in allmaterials.

It will be recognized thatthe difliculty men when working with sixtycycle alternating current, and, particularly, when working with currentsof higher frequency, the duration of each individual current shot of aninterrupted spot weld is very small, and the total time to complete thespot weld may only be a small fraction of a second. I havefound that thedie follow up with known apparatus is unsatisfactory for manyoperations, and can be materially improved.

Again, I have discovered in known methods and apparatus for electricresistance welding, and particularly spot welding, for example of theinterrupted type, that it is often difllcult to exactly time the startof flow of welding current to the electrodes at exactly the samepressure. This is true even though the fact is old and well known 1always closely follow and completely engage the that in order to obtainuniform welds pressure is one of the three variables, namely, time,pressure and current flow, which must be held at a constant figure inorder to obtain welds of a uniformly high grade character.

It is the general object of my invention to avoid and overcome theforegoing andother difficulties of and the objections to prior artmethods and apparatus by the provision of welding methods and apparatusparticularly adapted to electric resistance Welding, and specificallyspot welding, and in accordance with which materials which could notheretofore be satisfactorily and uniformly welded can now be welded in acompletely satisfactory manner and with a minimum of time, labor andexpense.

Another object of my invention is to provide an electrode mountinghaving a minimum of inertia and substantially no friction.

Another object of my invention is the provision of an. improved spotwelding apparatus and. methods particularly adapted to interrupted spotwelding operations. I

Another object of my invention is to provide an electric resistancewelding apparatus wherein rubber means are employed tomount at least oneof the cooperating dies, with the rubber means serving to store up thewelding pressure and to dispense it continuously and instantaneously tothe dies to obtain a substantially uniform welding pressure on the diesthroughout the complete duration of the welding operation regardless ofthe type of welding control utilized.

Another object of my invention is to provide welding apparatus includinga pair of electrodes mounted for relati e movement towards and from eachother, one of the electrode bein held so that rubber under shear stresstakes the welding thrust against the electrodes.

Another object of my invention is to provide means and methods forfiring or initiating the operation of welding apparatus of the typedescribed at exactly the same pressure of the electrodes against thework.

The foregoing and other objects of my invention are achieved by theprovision of a pair of cooperating electrodes, an auxiliary slidecarrying one electrode, a main slide, rubber mounting means carrying theauxiliary slide in association with the main slide, means for moving themain slide toward and from the other electrode to engage workbetweenethe electrodes and stress the rubber mounting means, means forsupplying welding current to the electrodes when the :rubber mountingmeans has been stressed to a selected pressure, means for opposing andreducing the pressure of the means moving the main slide and electrodestogether so that at the time welding current is first supplied to theelectrodes the pressure is a welding pressure only, and time delay meansassociated with the current supply means for substantiallyinstantaneously releasing the pressure opposing means after a given flowof welding current so that a forging of the weld under high pressure isobtained.

In accordance with the method of my invention I produce an interruptedtype of spot weld by moving a pair of welding electrodes into engagementwith opposed portions of the work to be welded, thereafter holding theelectrodes against the work by resilient rubber means and increasing thestress on the rubber means, passing a plurality of successive shots ofwelding supplying a flow of welding current to the electrodes so thatthe pressure of the electrodes against the work does not exceed amaximum welding pressure, and quickly releasing the lastnamed force aselected time interval after the start of the flow of welding current sothat the resulting increased force effects a forging action of the weld.

For a better understanding of my invention, reference should be had tothe accompanying drawings wherein Fig. 1 is a side elevation of one formof spot welding apparatus incorporating the principles of my'invention;Fig. 2 is a front elevation partly in section and on a larger scale, ofthe slide and slide mounting means shown in Fig. 1; Fig. 3 is ahorizontal crosssectional view taken on line Ill-III of Fig. 2; Fig. 4is a schematic wiring diagram of the apparatus shown in Figs. 1 to 3;and Fig. 5 is a schematic piping diagram of the apparatus shown in Figs.1 to 3.

It should be appreciated that the principles of my invention may beemployed with substantially any type of welding apparatus includingelectrodes or dies for contacting the work and adapted to direct a flowof electric current therethrough. However, my invention isparticularlydesigned for and is best utilized in conjunction with spot weldingapparatus including a pair of dies or electrodes adapted to be movedrelatively toward and from each other into and out of engagement'withthe work piece. Spot welding apparatus, of this character may take aplurality of forms as will be well understood by those skilled in theart. Accordingly, I have deemed it advisable to illustrate my inventionin conjunction with spot welding apparatus, and in the accompanyingdrawings I have shown one particular embodiment of such apparatus andincorporating the features of my invention.

Referring to the drawings, the numeral I0 indicates a housing of anupright rectangular suitable well known type therein, and which has asingle turn secondary I4. The front of the housing I0 -carries a platenIS in a normally fixed but vertically adjustable position, as forexample, by platen adjusting screws I8 and 20. Platen I8 is connected toone side of the secondary I4 of the transformer I2 and the platenadjustably carries a horn 22 which adjustably clamps a point, electrode,or die 24 which may be water cooled as by conduits 26.

Cooperating with the electrode or die 24 is a second point, electrode ordie 28 which is adjustably clamped in a horn 30 carried by a platen 32which is connected through suitable flexible conductors 34 to the otherside of the secondary I4 of the transformer I2. The platen 32 is securedto or formed integral with an inner or auxiliary slide, shown as a wholeby the numeral 40, and the inner slide is carried by a main slide 42 ofrectangular box-like shape which is provided with vertically directed,laterally extending gibs 44 which are slidably received in opposedgrooves formed in an upper arm or carrier bracket 46 secured to thehousing I0 in a position vertically above the lower platen I6.

The position of the main slide 42 in the upper bracket 45 isconveniently controlled by the use of a fluid pressure motor 50 mountedin a head portion 52 carried in the top of the bracket 48.

Having particular reference to Figs. 1, 2 and 5, the fluid pressuremotor 50 includes a cylinder 54 having its ends closed by headers 56 and58 which slidably receive through suitably packed openings piston rods60 and 62 respectively.

Piston rod 82 is secured to a yoke 64 which is fastened to the upper endof the main slide 42 by bolts 66. Piston rod 62 is secured at its otherend to a piston 68 of the double acting type. The piston rod 60 has adouble acting piston 10 secured to its lower end and the upper end ofthe piston rod 60 is threaded, as at 12, to adjustably receive aninternally threaded hub I4 having a hand wheel 16 secured thereto sothat by adjusting the hand wheel I6 the lowermost position of the piston10 in the cylinder 54 can be controlled.

Turning to Fig. 5, the piping arrangement for controllingthe operationof the fluid pressure motor 50 includes a manifold connected throughalubricator 82 and by way of a conduit 84 to a suitable source of fluidpressure. From the manifold 80 a. conduit 86 extends through a fluidpressure regulating valve 88, a threeway valve 90, and aspeed-controlvalve 92 to the inside of the piston rod 80 which is madehollow so that air or other fluid can flow down between the pistons-68and 10. A conduit 96 extends from the manifold 80 through a threewayvalve 98 and header 56 to the upper side of the piston 10. A conduit I00extends from the manifold 80 through a fluid pressure regulator valveI02, a pressure storage tank I04, and a three-way solenoid valve I06 tothe three-way valve 90. A fluid pressure gauge I08 and an atmosphericexhaust valve IIO are connected to the regulator I02. A conduit IIO alsoextends from the manifold 80 to a fluid pressure regulator H2, 2.pressure tank H4, 9. speed control valve IIS; a three-way solenoid valve8, through the header 58 to the underside of the piston 68. A pressuregauge I20 and atmospheric exhaust valve I22 are connected to theregulator valve II2.

Turning now to the manner in which the inner orauxiliary slide .40 ismounted in association with the main slide 42, and having parti-' cularreference to Figs. 1, 2 and 3, this is achieved with the aid of rubbercushioning .means Although various types of rubber cushioning means maybe employed, I have found those to be particularly advantageous in whichthe rubber is held under tension and absorbs the cushioning shocks intension. One excellent type of rubber cushioning means or unit of thecharacter indicated includes, as shown in the drawings, an innermetalsleeve I30 and a somewhat shorter, radially spaced outer metalsleeve I32 with an interposed body'of rubber I34 held between, the innerand outer sleeves and preferably vulcanized to each sleeve. Generally Iemploy a plurality of the rubber cushioning units in order to secure theinner slide 40 to the outer or main slide 42.

The upper platen 32 has secured thereto ina central and a verticallyextending position a post I36 which extends up centrally of the box ofthe main slide 42, with the bottom of the main slide 42 being aperturedas at I40 to receive the post leased as the die follow the work in thewelding operation.

Inbrder to properly center the inner or auxiliary slide 40 in the mainslide 42 at all times during the operation of the apparatus, and toprevent any side play of the inner slide in the main slide I preferablyprovide parallel linkage means which take the form of a pair of linksI80 which are pivotally secured at one end, as by pins I82, to thecentral post I36 of the inner slide 40 which is appropriately recessedto receive the links. The other end of the links I 80 are pivotallysecured, as by pins I84. to blocks I86 which are fastened to the back ofthe main slide 42 by. insulated bolts I88. Insulation I90 positionedbetween the blocks I86 and the main slide 42 together with the rubbermounting of the in-' ner slide in the main slide insures that none I36.The upper platen 32 is also formed with a plurality, usually four asshown, of apertured bosses I42 positioned substantially in a horizontalplane and at the four corners of the platen and adapted to receive boltsI44 to which the inner metal sleeves I of the rubber units are securedrespectively by means of a nut I46 and spacing washers I48 and I50.Ordinarily, the means for holding theouter metal sleeve, I32 of eachrubber cushioning unit comprises a cylinder I56 integral with the mainslide which cylinder is counterbored to receive the outer metal sleeveI32. The

cylinders I56 are positioned at the four lower corners of the main slideas illustrated. A locking ring I58 secured to the bottom of the mainslide 42 holds the outer metal sleeve I32 of each rubber cushioning unitsecurely in the main slide 42. The upper end of the post I36 is securedwith a rubber cushioning unit to the upper end of the main slide. Thisis accomplished by providing a cylinder I60 centrally of the upper endof the main slide 42 which cylinder is counterbored to pin 206 havingits lower end threaded and reand the upper end of the main slide 42, inthe manner shown in Fig. 2, provides an adjustment for the severalrubber cushioning units in the assembly. Particularly, when the bolt I68is tightened the central post I36 and upper platen 32 are moved upwardlywith respect to the main slide 42- and this places an initial tensionstress on each of the rubbercushioning units. By adjusting the degree ofthis tension the stiffness of the cushioning action provided by therubber units can be controlled.

' It will be understood that the construction of storing up the energyof the movement to be reof the welding current passed through the. upperplaten 32 becomes grounded on the frame of the apparatus. By positioningthe links I at spaced points vertically in the post I36, as best shownin Figs. 1 and 2 of the drawings, the post and thus the whole innerslide and upper platen 32 is given a parallel linkage mounting so thatit is properly centered within the main slide at all times even thoughthe die 28 is positioned at .a considerable distance off center from theupper platen 32. The movement of the inner slide in the main slide is inthe most extreme cases only relatively small so that the parallel linksI80 function in a completely satisfactory manner.

An important part of my invention is the provision of apparatus forfiring or initiating the welding operation at the same time in each oneof a series of welding operations and at a time when the pressure of thedies 24 and 280m the work is at a selected figure. Iachievethis in theembodiment of my invention illustrated by the provision of a deflectionmeter 200 which is mounted on the main slide 42 and which has the usualoutwardly extendingplunger 202 which is engaged by an insulated cap 204carried by a ceived in a tapped opening in a bracket 208 carried by theupper platen 32. The position of the pin 206 in the bracket 208 isadjusted so that during the operation of the apparatus any pressureapplied to the upperplaten 32 and causing upward movement of the innerslide with respect to the main slide 42 will create a deflectionmeasured by the meter'200 which can be calibrated either in pounds or infractions of an inch of deflection with the pressure of deflection beingread from a suitable chart.

On the front of the main slide 42 I mount a micrometer switch .2I2 whichis adapted to be operated by the upper end of a micrometer screw 2 I4and carried in a suitable bracket 2I6 secured to the upper platen 32.The upper end of the micrometer screw 2I4 carries an insulating cap 2I8so that the inner and main slides are maintained in insulated relationfrom each other.

Referring now to Fig. 4, the numeral 230 indicates a three phase inputconnection to the transformer control panel 232 associated withthewelding apparatus. The welding transformer I2 is connected to thecontrol panel 232 and the secondary of the transformer extends to theelectrodes 24 and 28. Also associated with the com trol panel 232 is thestarter control 234 which may be of either the hand or foot type andwhich is connected to operate the three-way solenoid valve I06. Themicro-switch 2I2 is connected to a relay 236 so that when themicro-switch 2I2 isclosed the relay 236 initiates the flow of currentfrom the control panel 232 through the welding transformer I2 and thussupplies the welding current to the electrodes 24 and 28. Also, therelay 236 operating through a sequence panel 238 and time controlmechanism therein operates the three way solenoid valve I I8 to effectthe application of the forging pressure a given time interval after thewelding operation has been initiated.

A more complete description of the operation of the apparatus will nowbe given. The fluid pressure motor 50 is first adjusted so that theproper die or electrode clearance is established for operations upon anygiven work piece. Specifically, it is desirable to have the electrodestravel only a relatively short distance into engagement with the work,and yet the electrodes must be capable of being moved relatively farapart so that operations can be performed upon the inside of flangedwork pieces and the like. Particularly, the hand wheel I6 is adjusted sothat the piston I normally limits the upward movement of the piston 58,with the upward limit of movement of the piston 68 being such that thework piece can be moved into welding position between the electrodes ordies with a minimum of clearance. It will be understood that theelectrode or die clearance should be kept as small as possible tofacilitate smooth opera-,

tion and speed of production. The piston I0 is normally held down to itslowermost position with the hub 74 of the hand wheel in engagement withthe header 56 by means of a relatively high fluid pressure, of say 200pounds per square inch passed to the upper side of the piston by conduit96 from manifold 80. The three way valve 98 connected in the conduit 86is adapted to open the upper side of the piston I0 to the atmospherewhen the handle 99 is. thrown at which time the piston I0 can be movedclear to the top of the cylinder 54. With the piston 10 at the top ofthe cylinder 54 the piston 68 can be raised considerably higher to givea relatively large clearance between the electrodes or dies to therebyallow the insertion of a work piece between the electrodes or dies eventhough the work piece has a relatively high upstanding flange or thelike with the weld to be performed on the inner side of the flange. I

Fluid under pressure is passed to the under side of the piston 68 by wayof conduit H0 and, in order to insure the type of action above generallyreferred to and hereinafter described in detail, the fluid pressureregulator valve I I2 is carefully set to provide a given fluid pressurein the tank II4 as indicated by the pressure gauge I20. The speedregulating valve III is set so that fluid, such as air, under a pressureof say 75 pounds per square inch is provided onthe under side of thepiston 08 which normally tends to hold the piston 00 up against theunder side of the piston I0.

Also, fluid under pressure is supplied through the conduit I00 to thefluid pressure regulatingpressure than the pressure on the fluid at theunder side of the piston 00, for example 150 pounds per square inch.Thus, when fluid under a pressure of say 150 pounds per square inch isapplied to the upper side of the piston 00, and fluid under pressure ofsay 75 pounds per square inch is applied to the underside of the piston68, the piston is forced downwardly by the differential in pressure. Itwill be understood that the three-way valve 90 provides a hand controlfor moving piston 68 downwardly to thus bring the dies together whereasthe three-way solenoid valve I00 is the automatic control normallyemployed in the usual operation of the apparatus.

A work piece of the size to be welded is now placed between theelectrodes 24 and 20 and the starter control 234 is operated to open thethreeway solenoid valve I06. Fluid under pressure then flows through theconduit I00 to the space between the pistons 60 and 10 to force thepiston and the upper die 28 carried thereby down against the uppersurface of the work which in turn forces the work down against the lowerdie 24. It will be seen that the greater pressure on the upper surfaceof the piston 00 and the lesser pressure on the under surface of thepiston 00 causes the piston to be forced. down by the difference betweenthese pressures and the areas over which they work. The exact value ofone or both of the pressures can be adjusted by means of the pressureregulating valves I02 and II! so that the exact differential pressure onthe upper electrode 20 can be very closely and accurately controlled togive the desired welding pressure on the dies or electrodes.

Now when the upper electrode or die 20 is forced down into engagementwith the work it will be recognized that the inner auxiliary slide 40including the upper platen 32 and the post I20 will be moved upwardly inthe main slide 42 against the cushioning action of the rubber meansmounting the inner slide in the main slide. The resistance of thecushioning action provided by the rubber mounting means is initiallyadjusted by the screw I00 so that the cushioning action can be still! orrelatively soft or any degree therebetween as desired for any givenwelding operation. The cushioningaction of the rubber should be suchthat the inner slide is moved up into the main slide a distance whichwill considerably more than cover the movement of the dies in followingthe work during the welding operation. When the inner slide is moved upinto the main slide in this manner the rubber units are cocked orstressed in shear so that they impart to the upper die the workfollowing characteristics hereinafter more particularly described.

It is sometimes diflicult to determine the exact diflerential weldingpressure eflective to move the dies together even though the diflerencebetween the pressures on the. gauges I00 and I20 can be readily takenwith the upper and lower surface areas of the piston 00 being known.However, due ,to fluctuationsin line pressure, temperature changes,lubrication diflerences, difficulty .of complete and accurate control ofpressures by pressure regulating valves I02 and I I2, and other reasons,it is highly advantageous to more directly determine the effectivepressure on the electrodes themselves. To this end, the deflection meter200 mounted on the side of the main slide 42 serves in conjunction .withthe adjustable pin 200 to give either a direct reading of the pounds ofdisplacement imparted to the rubber cushioning means, or the meter 200canmerely indicate the displacement effected between the inner slide 40friction and the inner slide possesses the mini-' and the main slide 42with the exact pressure being determined from a carefully calibratedgraph.

In all events, assuming that for a given job it has been found desirableto hold the dies against the work piece during the welding operationwith a pressure of say 2,000 pounds, the micrometer screw 2 i4 isaccordingly adjusted so that when the meter 200 reads 2,000 pounds themicro-switch 212 is closed. Thus, the welding operation is initiatedwith exactly the same pressure on the electrodes r dies over a longseries of welding operations, which is very important in order toachieve uniformity of welds.

It will be understood that the effective differ- 'ential in fluidpressure tending to move the upper electrode 28 down against the workpiece must be great enoughto stress the rubber cushioning means in shearto' the desired pressure to close the micro-switch 2| 2.- Usually, thedifferential in pressure is set by adjusting the pressure regulatorvalves I02 and 250 that the differential pressure is always great enoughto close microswitch 212 but is only a little greater. Closing themicro-switch 2l2 operates the relay 236 to initiate the flow of weldingcurrent from the control panel 232 through the transformer l2 and thencetothe electrodes 24 and 28. Also, microswitch 2l2 operating through therelay 236 starts into operation through the sequence control panel 238time delay mechanism which is adapted after a predetermined and selectedperiod to operate and open the three-way solenoid valve H8 to theatmosphere. As is evident from the drawings, the three-way solenoidvalve H8 is placed very close to the bottom of the cylinder 54 so thatthe discharge from the bottom of the piston 68 to the amosphere isrelatively short and direct. Thus, after a selected flow of weldingcurrent'through the electrodes with the electrodes being held togetherwith a welding pressure only, the force on the electrodes issubstantially instantaneously changed to .a forging pressure.Accordingly, a heavy forging pressure is applied to the electrodes, asfor example 4,000pounds and the weld is forged in a very rapid andpositive manner. I have found that it is possible .to change fromawelding pressure to a forging pressure in a much quicker and morepositive mannerby releasing a counteracting or opposing force, such asthe fluid pressure applied to the bottom of the piston 68, than ispossible when an attempt is made to increase the fluid pressure on thetop or upper side of the piston. It is often very important to effect analmost instantaneous change from the welding to the forging pressure asany slight delay is apt to result in the solidification of the weldbefore forging with the at-.

. tending difliculties of effecting true forgingrethe dies. due to theflow of electric current, the dies must closely follow and engage thework piece in order to obtain the best type of weld. I have found thatthe shear stressed cocked rubber cushioning means mounting the innerslide in the main slide possess substantially no mum of inertia beingmade as light as possible so that the upper-die 28 very closely followsthe work piece and keeps the work piece down in very intimate contactwith the lower die 24.

, Thus, there is no burning or substantial change .with periods when nowelding current flows but in resistance of the contact between theelectrodes and the work piece during the entire welding operation. Ifthere is considerable movement of the dies into the work piece duringthe welding operation the main slide. 42 may follow down also under theinfluence of the fluid pressure, however, no movement of the main slideis ordinarily required.

I have found that the action just described is advantageous and providesa particularly high grade, uniform and improved type of weld uponordinary material when spot welded in a noninterrupted manner. Butparticularly, my improved apparatus and die mounting means is adapted tointerrupted spot welding operations, sometimes called pulsation'weldingor persistence welding. In welding operations of this character the diesare first engaged with the work and the work is given a series of shotsof welding current, each shot of current being interspersed during whichthe dies remain in constant engagement with the work.- Much heaviergauge stock can be spot or mash welded in this manner.

" Also, by this method, rusty or scaly stock can often be welded withoutcleaning.

Various .types of controls for interrupted spot welding have beenprovided. For example, vacuum tube controls have been used in which the'welding current is allowed to be on for a fraction of a cycle or aplurality of cycles with the current being then interrupted for afraction of a cycle up to a, plurality 'of cycles, and with theoperation being repeated any desired number of times. Also, capacitorsmay be employed in the welding circuit which are charged for a fractionof a cycle up to a plurality of cycles followed by a discharge of thecapacitors for a fractionof a cycle or a plurality of cycles. In a timecontrol of the type described, even with sixty cycle operation the timein which the dies must follow the work in interrupted spot welding isvery short. When the same or a similar type of interrupted spot weldingemploys current of high frequencies the time in which the dies must movebecomes proportionately shorter and this is true regardless of the exacttype of control for the welding operation.

I have discovered that the rubber cushioning means disclosed hereinprovide a very quick and improved follow up of the dies in substantiallyany type of spot welding operation, and, particularly, interrupted spotwelding operations, and specifically those of higher frequencies. Ibelieve that the follow up actionwhich my improved apparatus providesresults in a weld forging action totally lacking in many spot weldingoperations performed or attempted to be performed heretofore. In fact,the weld follow up and associated forging action provided is quitedifferweld at the proper pressure regardless of whether the weld is madewith high or low frequency alternating current or direct current, or ismade interrupted or non-interrupted. Thus, when the improved actionprovided by the rubber cushioning means is combined with the almostinstantaneous change from welding to forging pressures, as effected bythe release of the pressure on the under side of the piston 68, a forgedweld can be obtained upon relatively thin aluminum and many othersimilar materials which has heretofore been either very dimcult toachieve in a satisfactory manner or has been impossible to produce.

The welding cycle'is completed by closing solenoid valve H8 to againapply fluid pressure to the under side of the piston 68, and openingsolenoid valve I to the atmosphere. These operations are controlledautomatically from the panels 232 and 238 and return the piston 68 upagainst the under side of piston l0. Thus, the apparatus is ready foranother complete cycle of welding operations as already described.

From the foregoing it will be recognized that the various objects of myinvention have been achieved by the provision 01' a relativelyinexpensive and simple but durable and long wearing Welding apparatuswherein electrodes or dies are mounted in an improved manner so thatthey will very closely engage, follow and forge the work during awelding operation. Lubrication of the inner metal slide in the mainslide is eliminated,

and the adjustment of the "cocking and cushioning action provided by therubber means is quick and simple. The apparatus can be quickly adaptedto operations upon a wide variety of materials necessitating welding andforging pressure of considerably difierent values and operations can beperformed upon materials having upstanding flanges or other interruptingportions in a rapid and eflicient manner. The welding operation isinitiated .at exactly the same pressure in each one of a plurality ofwelds and this pressure can be readily and accurately adjusted so thatfiring or the welder occurs at the exact instant desired. Thus a longstride has been taken to eliminate variables and fluctuating conditionsin the production or electric resistance welds and the result is theproduction of more uniform and definitely improved welds. The principlesof my invention adapt themselves to use with substantially any type ofwelding apparatus, and maintenance and repair are at a minimum.

The exact number, size and position of the in- I dividual rubbercushioning units may be widely varied to best adapt them to anyparticular apparatus or welding requirement. Preierably I construct allof the inner slide parts of the lightest weight metal afiording therequisite strength so that the inertia thereof will be kept at aminimum. Also, it will be recognized that in certain instances the fluidpressure motor can be dispensed with and other means provided for movingthe electrodes together.

While in accordance with the patent statutes I have particularlyillustrated and described one embodiment of my invention, it will beunderstood that I am not to be limited thereto or thereby but that thescope of my invention is defined in the appended claims.

What I claim is:

1. Electric resistance welding apparatus of the type including a pair ofelectrode dies, and means for moving the dies relatively toward and fromeach other, and characterized by rubber mounting means for one of thedies and resiliently supporting the die in the direction of relativemovement, said rubber mounting means serving ,also to insulate theresiliently mounted die from the remainder oi the apparatus.

2. Electric resistance welding apparatus or the type including a pair ofelectrode dies, and means for moving the dies relatively toward and fromeach other, and characterized by a plurality of rubber mounting meansfor one of the dies and resiliently supporting the die at spaced pointsin the direction of relative movement, the rub- I her in said mountingmeans being under tension when welding pressure is applied to the dies.

3. In combination in electric resistance welding apparatus, a normallystationary die, a cooperating die, a movable member, and a plurality ofrubber units mounting the cooperating die in the movable member, eachunit including inner and outer metal sleeves and a body or rubbervulcanized to and between the sleeves.

4. In combination in electric resistance welding apparatus, a normallystationary die, a cooperating die, a movable member, a plurality oirubber units resiliently mounting the cooperating die in the movablemember, certain of said units being mounted so that their ends liesubstantially in a plane and at least one of the units being mountedcentrally of the aforesaid units and in a position offset from butnormal to the said plane, and parallel linkage means centering thecooperating die in the movable member.

5. An electric resistance welding apparatus of the type including a pairof electrode dies, and means for moving the dies relatively toward andfrom each other, and characterized by rubber mounting means for at leastone or the dies and electrode in the direction or relative movement.

MALCOLM B. CLARK

